1,084 research outputs found
'Breaking the glass': preserving social history in virtual environments
New media technologies play an important role in the evolution of our society. Traditional museums and heritage sites have evolved from the ‘cabinets of curiosity’ that focused mainly on the authority of the voice organising content, to the places that offer interactivity as a means to experience historical and cultural events of the past. They attempt to break down the division between visitors and historical artefacts, employing modern technologies that allow the audience to perceive a range of perspectives of the historical event. In this paper, we discuss virtual reconstruction and interactive storytelling techniques as a research methodology and educational and presentation practices for cultural heritage sites. We present the Narrating the Past project as a case study, in order to illustrate recent changes in the preservation of social history and guided tourist trails that aim to make the visitor’s experience more than just an architectural walk through
An inverse method for determining the spatially resolved properties of viscoelastic–viscoplastic three-dimensional printed materials
A method using experimental nanoindentation and inverse finite-element analysis (FEA) has been developed that enables the spatial variation of material constitutive properties to be accurately determined. The method was used to measure property variation in a three-dimensional printed (3DP) polymeric material. The accuracy of the method is dependent on the applicability of the constitutive model used in the inverse FEA, hence four potential material models: viscoelastic, viscoelastic–viscoplastic, nonlinear viscoelastic and nonlinear viscoelastic–viscoplastic were evaluated, with the latter enabling the best fit to experimental data. Significant changes in material properties were seen in the depth direction of the 3DP sample, which could be linked to the degree of cross-linking within the material, a feature inherent in a UV-cured layer-by-layer construction method. It is proposed that the method is a powerful tool in the analysis of manufacturing processes with potential spatial property variation that will also enable the accurate prediction of final manufactured part performance
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Energy Inputs to Additive Manufacturing: Does Capacity Utilization Matter?
The available additive manufacturing (AM) platforms differ in terms of their
operating principle, but also with respect to energy input usage. This study presents an
overview of electricity consumption across several major AM technology variants, reporting
specific energy consumption during the production of dedicated test parts (ranging from 61 to
4849 MJ per kg deposited). Applying a consistent methodology, energy consumption during
single part builds is compared to the energy requirements of full build experiments with
multiple parts (up to 240 units). It is shown empirically that the effect of capacity utilization
on energy efficiency varies strongly across different platforms.Mechanical Engineerin
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A Hybrid Algorithm for Topology Optimization of Additive Manufactured Structures
Most topology (TO) algorithms involve the penalization of intricate structural features to eliminate manufacturing difficulties. Since additive manufacturing is less dependent on manufacturing
constraints, it becomes necessary to adapt these algorithms for AM. We propose a hybrid algorithm
consisting of an adaptive meshing strategy (AMS) and a modified form of the bidirectional evolutionary structural optimization (BESO) method. By solving a standard cantilever problem, we show
that the hybrid method offers improved performance over the standard BESO method. It is proposed
that the new method is more suitable for optimizing structures for AM in a computational efficient
manner.Mechanical Engineerin
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Fatigue Performance Enhancement of Selectively Laser Melted Aluminum Alloy by Heat Treatment
We measured the stress-strain behaviour and fatigue performance of the aluminium
alloy Al-Si10-Mg manufactured by selective laser melting (SLM). This process, specifically the rapid cooling of the metal from its molten state, results in a fine microstructure, generally providing high hardness but poor ductility. We used a heat treatment
to alter the microstructure of the material from its as-built state. This significantly
improved the ductility and fatigue performance. The elongation at break for the heat
treated material was nearly three times greater than that observed for the as-built
material, and the fatigue strength at 106
cycles was around 1.6 times as high. Combined with the design freedoms of additive manufacture, this development increases
the suitability of lightweight SLM parts for use in the aerospace and automotive
sectors, where good fatigue performance is essential.Mechanical Engineerin
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3D-Inkjet Printing of Flexible and Stretchable Electronics
Inkjet printing of conductive tracks on flexible and stretchable materials have gained
considerable interest in recent years. Conductive inks including inks with silver nanoparticles, carbon based inks, inks containing poly (3,4-ethylenedioxythiophene) (PEDOT)
doped with polystyrene sulfonic acid (PSS) are being researched widely to obtain a printed
electronic patterns. In this study, we present drop-on-demand inkjet printing of conductive
silver and PEDOT:PSS on a flexible and stretchable substrate. Process conditions for the
inkjet printing of silver nano-particles and PEDOT:PSS were optimised and simple
geometrical patterns (straight line and sinewave tracks) were printed. Surface profile, surface
morphology and electrical resistance of the printed patterns were examined. The printed
silver patterns were observed to be highly conductive; however when stretched, the patterns
did not conduct due to the origination of cracks. The measured conductivity for the
PEDOT:PSS patterns was significantly lower than the silver patterns; however, they
remained conductive when stretched for up to 3 mm. When flexed, PEDOT:PSS remained
conductive for a lower radius of curvature (10 mm) than the silver. Among the printed
patterns, the sinewave pattern was observed to be superior for flexible electronics application.Mechanical Engineerin
Mechanisms of Phosphine Toxicity
Fumigation with phosphine gas is by far the most widely used treatment for the protection of stored grain against insect pests. The development of high-level resistance in insects now threatens its continued use. As there is no suitable chemical to replace phosphine, it is essential to understand the mechanisms of phosphine toxicity to increase the effectiveness of resistance management. Because phosphine is such a simple molecule (PH3), the chemistry of phosphorus is central to its toxicity. The elements above and below phosphorus in the periodic table are nitrogen (N) and arsenic (As), which also produce toxic hydrides, namely, NH3 and AsH3. The three hydrides cause related symptoms and similar changes to cellular and organismal physiology, including disruption of the sympathetic nervous system, suppressed energy metabolism and toxic changes to the redox state of the cell. We propose that these three effects are interdependent contributors to phosphine toxicity
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The BCC Unit Cell for Latticed SLM Parts; Mechanical Properties as a Function of Cell Size
The existing framework describing the mechanical properties of lattices places strong
emphasis on one important property, the relative density of the repeating cells. In
this work, we explore the effects of cell size, attempting to construct more complete
models for the performance of lattices. This was achieved by examining the elastic
modulus and ultimate tensile strength of latticed parts with a range of unit cell sizes
and fixed density. The parts were produced by selective laser melting (SLM). The
examined cell type was body-centred-cubic (BCC), a cell of high relevance for SLM
because of its self-supporting structure. We obtained power law relationships for the
mechanical properties of our latticed specimens as a function of cell size, which are
similar in form to the existing laws for the density dependence. These can be used
to predict the properties of latticed column structures comprised of BCC cells, and
may be easily amended for other situations. In addition, we propose a novel way to
analyse the elastic modulus data, which may lead to more general models, applicable
to parts of varying size. Lastly, our general methodology may be of use in future
studies which explore the other parameters that determine lattice performance; the
choice of cell type, the global shape of the lattice structure and the type of stress.Mechanical Engineerin
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High Viscosity Jetting System for 3D Reactive Inkjet Printing
High viscosity ink is a potential solution for the improvement of current 3D ink jetting
technology. In this study, experiments are carried out to study a series of inks with differing
viscosities jetted with PicoDot™ jet valves under different process parameters of temperature
and pressure. Results show that a wide range of ink materials from low viscosity (water like
materials) to very high viscosity (thixotropic materials) can be jetted with the piezoelectric
actuated jet valves without the need of solvents and surfactants. The jetting volume can be
controlled under certain conditions between 2nl and 15nl. The jetting performances for low,
medium and high viscosity inks have been recorded by high-speed video photography.Mechanical Engineerin
Residual disorder and diffusion in thin Heusler alloy films
Co2FeSi/GaAs(110) and Co2FeSi/GaAs(111)B hybrid structures were grown by
molecular-beam epitaxy and characterized by transmission electron microscopy
(TEM) and X-ray diffraction. The films contained inhomogeneous distributions of
ordered L2_1 and B2 phases. The average stoichiometry was controlled by lattice
parameter measurements, however diffusion processes lead to inhomogeneities of
the atomic concentrations and the degradation of the interface, influencing
long-range order. An average long-range order of 30-60% was measured by
grazing-incidence X-ray diffraction, i.e. the as-grown Co2FeSi films were
highly but not fully ordered. Lateral inhomogeneities of the spatial
distribution of long-range order in Co2FeSi were found using dark-field TEM
images taken with superlattice reflections
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